In individuals with substantial damage to the central nervous system (“CNS”), the traditional understanding has been that the damaged CNS tissue cannot readily regenerate. As a consequence, it has been further understood that the possibility of substantial recovery of daily life functional capabilities is highly unlikely in individuals with severe paralysis of the legs and/or arms caused by CNS diseases such as strokes, spinal cord injuries, and traumatic brain injuries.
New hope for individuals with CNS damage has been provided by recent research studies demonstrating regeneration of substantially damaged CNS pathways controlling the sensory and motor activities of the limbs (Taub Edward, PhD; Gitendra Uswatte, MA; Rama Pidikiti, MD. Constraint-Induced Movement Therapy: A New Family of Techniques with Broad Application to Physical Rehabilitation—A Clinical Review. Journal of Rehabilitation Research and Development 1999; 37). Frequent stimulation of damaged neural pathways has been cited as a critical factor to CNS tissue regeneration. For individuals with paralysis concentrated in the limbs on one side of the body, one approach to providing the necessary stimulation therapy is to force the subject to use the impaired limbs by constraining use of the unimpaired ones while the patient performs simple tasks. For individuals with incomplete bilateral paralysis, including paraplegic and quadriplegic injuries, spastic paralysis, multiple sclerosis, stroke, and traumatic brain injuries, locomotion therapy using a treadmill and a partial weight bearing harness has become an accepted standard of care (Rossignol IS, Barbeau H. New approaches to locomotor rehabilitation in spinal cord injury. Annals of Neurology 1995;37(5):555–556). In this type of therapy, the overhead harness system supports the patient sufficiently such that the motion of the treadmill belt assists the patient in moving the legs in a locomotor-like pattern. Such partial weight bearing treadmill methods are of proven clinical value in restoring the ability to move and walk in patients with unilateral paralysis and/or with sufficient residual function to generate a minimum level of limb movement in response to the treadmill belt motion (Dobkin BH. An overview of treadmill locomotor training with partial body weight support: a neurophysiologically sound approach whose time has come for randomized trialy. Neurorehabilitation and Neuronal Repair 1999; 13(3): 157–164).
For individuals with more severe bilateral paralysis involving the two legs, forced use of the impaired limbs and treadmill-based locomotion therapies are impractical and potentially unsafe. The patient is too impaired to move the legs independently while either freely standing or suspended over a moving treadmill belt. In these cases, stimulation therapy can be provided only by externally imposing movements of the legs in repetitive patterns resembling daily life activities such as walking.
The effectiveness of providing stimulation to individuals with bilateral paralysis by externally imposed movements of the impaired limbs has been dramatized in popular press descriptions of Christopher Reeves' medical situation. Reeves, an actor famous for his film portrayal of Superman, suffered a complete section of his spinal cord resulting in total paralysis and loss of sensation below the neck. Despite the conventional belief that his paralysis was permanent and complete, Reeves has undergone imposed movement stimulation therapy as administered by a team of clinicians for several hours per day, resulting in measurable recovery of sensory and motor function in the legs.
There are practical and technical barriers to widespread treatment of severe stroke, spinal cord injury, and traumatic brain injury patients using externally imposed movement therapy similar to that used with Reeves. When the movement therapy is provided manually, the therapy requires multiple clinicians for multiple hours per day to manipulate the limbs, making the cost of such therapy prohibitive. Even with the patient suspended on a moving treadmill belt, the assistance of multiple clinicians to manually move the legs is required, since movement of the treadmill belt alone does not result in stepping-like leg motions.
In response to increased interest in the use of imposed movement therapy, two manufacturers have developed partial weight bearing treadmill systems that include mechanically powered appendages that can automatically move the legs through pre-programmed patterns of movement. One of these devices, the “AutoAmbulator”manufactured by HealthSouth Corporation of Birmingham, AL, is described at www.healthsouth.com/medinfo/home/app.
The HealthSouth website describes the AutoAmbultor as including an overhead harness system able to fully or partially support a subject's weight, two mechanically motorized braces to move each of the subject's legs, computerized sensors to track the subject's vital signs, leg motions and speed of leg movements, devices that permit automatic belt speed adjustments based on leg movement speed, and emergency controls that permit the subject or therapist to stop the machine. The site further describes the ability of the machine to mimic the proper human gait as well as to provide the clinician with the above described data to monitor patient progress.
The HealthSouth website also provides two studies. The first study describes a normal subject walking on the AutoAmbulator system with partial weight support while wearing a tight nylon suit fitted with reflectors. The positions of the reflectors over time are recorded by a computer-video based motion analysis system. The purpose of the first study is to measure the subject's leg motions during robotic patterning and to compare the patterned motions to those produced by the same subjects during normal unassisted walking on the treadmill. The second study uses x-ray imaging techniques to analyze the position of the lower back while normal subjects are suspended in the harness six inches above the treadmill and while wearing the harness with the feet on the treadmill. The purpose of the second study is to assure that the harness system does not cause potential harm to the lower back.
A second partial weight bearing treadmill device incorporating a robotic appendage to provide patterns for movement of the legs is the LOKO System® manufactured jointly by Woodway GmbH of Weil am Rhein, Germany, and Hocoma AG of Zurich, Switzerland. The LOKO System, as described at the website www.woodway.com/LOKO_new.htm, is an open treadmill and partial weight bearing harness in which the patient can be led through locomotion therapy either with the clinician manipulating the patients leg movements or with the leg movements imposed automatically by an motorized appendage.
A number of devices and methods for measuring the forces and motions of the legs during free walking and walking on a treadmill have been described in the prior art. Examples of devices for recording the motions of the legs and body using computer-video techniques include systems manufactured by MotionAnalysis Corporation of Santa Rosa, Calif. and Vicon Ltd. of Oxford, United Kingdom, Lake Forest, Calif. and Hong Kong. Advanced Mechanical Technology, Inc. of Watertown, Mass. markets forceplates that can be mounted in the surface over which a subject walks to document the forces of the feet during human balancing and walking. The Balance Master system manufactured by NeuroCom International, Inc. of Clackamas, Oreg. uses a five-foot long forceplate to record the timing and positions of successive foot placements during locomotion. U.S. Pat. No. 5,474,087, U.S. Pat. No. 5,623,944, and U.S. Pat. No. 6,010,465 (each of which are hereby incorporated herein by reference) describe a treadmill device incorporating at least two forceplates under the moving belt to record the forces of the two legs independently during treadmill walking. GaitRite, a pressure sensitive mat manufactured by CIR Systems Inc. of Clifton, N.J. can measure the locations and timing of the successive steps of a walking subject.